feat(author): cache commit authors for an hour

so that we don't keep on doing the same API calls to github

src/composition-root.ts

@@ -2,6 +2,7 @@ import { ConstructorFunction, IControllerFactory } from './api/ioc/IControllerFa
 import { MetaInfo, meta as metaFromPackageJson } from './meta';
 import { BearerAuthenticationProvider } from './api/auth/BearerAuthenticationProvider';
 import { BuildInfoController } from './api/controllers/BuildInfoController';
+import { CachedCommitAuthorRepository } from './infra/caching/CachedCommitAuthorRepository';
 import { CachedRepoRepository } from './infra/caching/CachedRepoRepository';
 import { CommitAuthorRepository } from './infra/github/CommitAuthorRepository';
 import { Controller } from '@tsoa/runtime';
@@ -21,9 +22,6 @@ import { UserRepository } from './infra/github/UserRepository';
 import { WorkflowRunRepository } from './infra/github/WorkflowRunRepository';
 import { getOctokitFactory } from './infra/github/OctokitFactory';
 
-const SERVER_PREFIX = 'gha-build-monitor';
-const SERVER_NAME = 'gha-build-monitor';
-
 export interface ApiDependencies {
   readonly userRepo: IUserRepository;
   readonly repoRepo: IRepoRepository;
@@ -55,7 +53,10 @@ export class CompositionRoot implements IControllerFactory {
       repoRepo: new RepoRepository(octokitFactory),
       workflowRunRepo: new WorkflowRunRepository(
         octokitFactory,
-        new CommitAuthorRepository(octokitFactory)
+        new CachedCommitAuthorRepository(
+          new LRUCache<string, any>({}),
+          new CommitAuthorRepository(octokitFactory)
+        )
       ),
     });
   }

src/infra/caching/CachedCommitAuthorRepository.ts

@@ -0,0 +1,27 @@
+import { CommitAuthor, ICommitAuthorRepository } from '../github/CommitAuthorRepository';
+import LRUCache from 'lru-cache';
+import { RepoName } from '../../domain/IRepoRepository';
+
+export class CachedCommitAuthorRepository implements ICommitAuthorRepository {
+  public constructor(
+    private readonly cache: LRUCache<string, any>,
+    private readonly wrapped: ICommitAuthorRepository
+  ) {}
+
+  public async getAuthorForCommit(
+    token: string,
+    repoName: RepoName,
+    commitId: string
+  ): Promise<CommitAuthor | null> {
+    const cacheKey = `${repoName.fullName}/commit(${encodeURIComponent(commitId)})`;
+    const existing = this.cache.get(cacheKey);
+
+    if (existing !== undefined) {
+      return existing as CommitAuthor | null;
+    }
+
+    const actual = await this.wrapped.getAuthorForCommit(token, repoName, commitId);
+    this.cache.set(cacheKey, actual, 60 * 60 * 1000); // cache for an hour
+    return actual;
+  }
+}